I propose to determine the primary structure of a group of mouse antibodies which bind streptococcal group A carbohydrate (GAC), and the structure and organization of genes which encode these antibodies. The amino acid sequence of anti-GAC antibody heavy (H) and light (L) chains derived from hybridomas will be determine using the automated sequenator and by sequencing hybridoma mRNA. Using recombinant DNA technology, germ-line gene segments encoding the variable regions of anti-GAC H and L chains will be identified and the primary structure of these determined. As it is expected that multiple gene segments exist in the germ line for this group of antibodies, attempts will be made to determine the organization of these segments in germline DNA, and the extent of reorganization of the same segments in hybridoma DNA. This detailed analysis of a group of antibodies with similar specificities is designed to evaluate, 1) the extent to which combinatorial diversity of H and L polypeptide chains contributes to overall binding site diversity in the response to a common environmental antigen, 2) the degree of sequence variability in a well-defined set of h and L chains and possible mechanisms by which this sequence variability may be generated, and 3) the extent to which genes encoding H and L chain variable regions are coordinately expressed. The focus of this proposal is the organization of mouse antibody genes, the rules that govern expression of these genes, and more broadly, the mechanisms which regulate gene expression in multigene families.